This invention relates to a process for the pretreatment of light hydrocarbons to remove sulfur, water and oxygen-containing compounds. More specifically, the invention concerns subjecting a light hydrocarbon feed containing C.sub.4 -C.sub.8 hydrocarbons to a first adsorption zone comprising a molecular sieve and then to a second adsorption zone comprising an activated alumina. The invention finds utility as a pretreatment process for a light hydrocarbon isomerization process.